The present invention relates to a radio communication apparatus, such as a telephone set, for use in combination with a terminal unit.
A recent technical development has brought about a telephone set which has various user interface functions. In one of the user interface functions, the telephone set is used in combination with a selected terminal unit which is selected from a plurality of terminal units of different kinds and is of a selected kind. The telephone set includes a receiving part for receiving a radio signal to produce a received signal and an adjusting part for adjusting the received signal to produce an adjusted signal. The selected terminal unit is provided with an ear piece receiver or an announcing unit for providing an announce signal by generating an audible signal having an adjustable volume which can be adjusted in accordance with the adjusted signal.
Various handsets of different kinds have been developed as the terminal units for the telephone set. A handset of a first one of the kinds comprises a control unit for producing an announce control signal which can be adjusted in response to operation of a volume key. Responsive to the announce control signal, the telephone set controls the audible signal. It is necessary for the first kind of handset that the adjusted signal has a first selected level.
Another handset of a second kind is provided with an adjustable volume member for adjusting the volume of the audible signal independently of the telephone set and is inexpensive. It is necessary for the second kind that the adjusted signal have a second selected level which is different from the first selected level.
In addition, it is possible to use, as the selected terminal unit, a handset which comprises a loudspeaker. When this handset is used as the selected terminal unit, it is unnecessary in carrying out communication for an operator to hold the handset with his hands, the so-called "hands free" type device. In this event, it is necessary that the adjusted signal have a third selected level which is different from each of the first and the second selected levels.
Accordingly, it is desired that the adjusted signal be automatically adjusted to have a level which is suitable for the selected terminal unit.